1. Field of the Invention
The present invention relates to a zoom lens and an image pickup apparatus equipped with the same.
2. Description of the Related Art
In recent times, digital cameras that pick up an image of an object using a solid state image pickup element such as a CCD or CMOS have replaced film cameras and become the mainstream. Furthermore, various categories of digital cameras ranging from popular-priced compact type cameras to function-rich cameras for professionals have been developed.
Users of popular-priced digital cameras wish to enjoy easy shooting in various shooting situations anywhere at any time. For this reason, such users tend to favor small size digital cameras, especially slim digital cameras that can be conveniently carried in a pocket of clothes or a bag. Therefore, a further reduction in the size of the taking lens system is demanded.
On the other hand, there is a trend toward an increase in the number of pixels of image pickup elements, and high optical performance consistent with the increased numbers of pixels of image pick up elements are demanded. Furthermore, while zoom lenses having zoom ratios higher than 10 have been developed to widen the variety of shooting and have become popular, a further increase in the zoom ratio is expected.
Digital cameras capable of performing image processing for extending the sensitivity range or dynamic range to enable shooting in high-contrast situations have also been developed, enabling shooting without limitations in situations.
In shooting in dark places, while contrast can be corrected electronically to some extent, use of a large-diameter lens or a fast lens allows shooting in darker places and will increase the variety of scenes that can be shot.
Since fast, large-diameter lenses enable clear image shooting even with small incident light quantities, they can provide increased choice, such as higher shutter speeds in continuous shooting of a moving object, to photographers. For this reason, large-diameter lenses have been receiving attention in recent times.
As a prior art zoom lens having a relatively high zoom ratio and high speed (or small F-number) throughout the entire focal length range from the wide angle end to the telephoto end, a zoom lens including, in order from the object side, a positive first lens unit, a negative second lens unit, a positive third lens unit, negative fourth lens unit, and a positive fifth lens unit have been known (Japanese Patent Application Laid-Open No. 2008-304706).